I. Field of the Invention
The present invention is directed generally to catheter systems utilizing inflatable balloon dilatation devices for mechanical dilation of vascular stenoses and, more particularly, the invention addresses improvements in such systems related to the perfusion or bypassing of vessel fluid during such procedures to overcome limitations associated with the disruption of blood supply beyond the ditilation device that accompanies balloon expansion. Specifically, the invention deals with improvements in side opening flow passage arrangements including openings distal and proximal of the balloon in fluid communication with one another via a continuous lumen extending through and beyond the balloon.
II. Related Art
Percutaneous dilatation of arterial stenoses, particularly coronary artery stenoses, using a balloon dilatation catheter has become a recognized and common procedure that has proved to be effective in many instances. Inflation of the balloon to depress stenoses results in the obstruction of blood flow through the vascular passage of interest during the inflation. This, of course, is undesirable from the standpoint of loss of blood supply delivered to downstream tissues thus deprived. To prevent damage to these tissues, the inflation period of the balloon is limited to the time frame of about 2-3 minutes, after which the balloon must be deflated and flow allowed to pass to avoid tissue damage or even necrosis.
The dilatation time can be significantly lengthened, however, without increased risk of ischaemia by the provision of a bypass or perfusion system in which a passage is provided through the inflated balloon that enables vessel fluid flow to continue uninterrupted during the inflation or dilatation period.
Systems have been devised which include the provision of a perfusion path in dilatation catheters. One such system is illustrated and described in U.S. Pat. No. 5,201,723 to Quinn which incorporates a pattern of opposed elongated holes inclined and arranged to prevent kinking of the catheter. Another system is shown in U.S. Pat. No. 5,295,961 to Niederhauser et al that includes side openings connecting the vascular lumen with a common interior catheter lumen. The openings are arranged both distal and proximal of the balloon and the common catheter lumen extends through and beyond the balloon and are substantially perpendicular or normal to the longitudinal axis of the catheter in both the proximal and distal locations. The contents of U.S. Pat. No. 5,295,961 are deemed incorporated herein by reference for any purpose. While that system has accomplished perfusion and has met with a great deal of success, it would be more advantageous to provide a system that enjoys reduced pressure drop across the balloon system and reduces any tendency toward turbulent flow. In addition, severe directional changes and relatively sharp inlet and outlet opening edges may result in injury to blood cells as they negotiate the perfusion flow system. In this regard, it would be advantageous to provide an improved perfusion flow system in a dilatation catheter system which not only reduces pressure loss across the dilatation catheter and reduces the tendency toward turbulent flow, but which also provides a safer ingress and egress for the blood cells negotiating the system.
Accordingly, it is a primary object of the present invention to provide a perfusion flow system for a dilatation catheter which reduces the pressure drop across the balloon catheter and also reduces the tendency toward turbulent flow.
A further object of the present invention is to provide a perfusion flow arrangement for a dilatation catheter that reduces the tendency for blood cells negotiating the system to be damaged.
A still further object of the present invention is to provide a perfusion flow system for a dilatation catheter that maintains a blood flow of at least 40 cc/min. at about 80 mm Hg proximal perfusion pressure.
Other objects and advantages of the invention will occur to those skilled in the art upon familiarization with the description and accounts contained in the specification, together with the appended claims.